The alpha-crystallins compose a large fraction of the soluble protein in th vertebrate lens, where they are believed to function as structural proteins are the first crystallins to be expressed in the developing mouse lens; and are a relatively small family of crystallins encoded by only two genes, the alphaA- and `B-crystallin genes. The alpha-crystallins exhibit molecular chaperon activity and kinase activity and, at least in the case of alphaB- crystallin, have been shown to be expressed in a variety of nonlenticular tissues, where their function is unknown. Toward understanding the role of the alpha-crystallins in lens and nonlens tissues, we are attempting to functionally delete `-crystallins by disrupting their genes in mice. We ar using the technique of homologous recombination in pluripotent mouse embryonic stem cells followed by generation of chimeric mice containing the altered stem cells. We have isolated and mapped 15 kb clones containing th alphaA- and alphaB-crystallin gene loci from a mouse 129SV library (the same strain as most of the embryonic stem cell lines currently in use). Construction of alphaA-crystallin, alphaB-crystallin, and alphaA-CRYBP1 knockout vectors is complete. We are mastering the technologies to (1) effect homologous recombination in embryonic stem (ES) cells and (2) introduce ES cells into embryos that develop into chimeric mice. In collaboration with Nicholas Ambulos (University of Maryland Medical School) we are sequencing the mouse alphaA-crystallin gene locus.